(function(win, lib) {
	var doc = win.document;
	var docEl = doc.documentElement;
	var metaEl = doc.querySelector('meta[name="viewport"]');
	var flexibleEl = doc.querySelector('meta[name="flexible"]');
	var dpr = 0;
	var scale = 0;
	var tid;
	var flexible = lib.flexible || (lib.flexible = {});

	if (metaEl) {
		console.warn('将根据已有的meta标签来设置缩放比例');
		var match = metaEl
			.getAttribute('content')
			// eslint-disable-next-line no-useless-escape
			.match(/initial\-scale=([\d\.]+)/);
		if (match) {
			scale = parseFloat(match[1]);
			dpr = parseInt(1 / scale);
		}
	} else if (flexibleEl) {
		var content = flexibleEl.getAttribute('content');
		if (content) {
			// eslint-disable-next-line no-useless-escape
			var initialDpr = content.match(/initial\-dpr=([\d\.]+)/);
			// eslint-disable-next-line no-useless-escape
			var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/);
			if (initialDpr) {
				dpr = parseFloat(initialDpr[1]);
				scale = parseFloat((1 / dpr).toFixed(2));
			}
			if (maximumDpr) {
				dpr = parseFloat(maximumDpr[1]);
				scale = parseFloat((1 / dpr).toFixed(2));
			}
		}
	}

	if (!dpr && !scale) {
		// eslint-disable-next-line no-unused-vars
		var isAndroid = win.navigator.appVersion.match(/android/gi);
		var isIPhone = win.navigator.appVersion.match(/iphone/gi);
		var devicePixelRatio = win.devicePixelRatio;
		if (isIPhone) {
			// iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
			if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
				dpr = 3;
			} else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
				dpr = 2;
			} else {
				dpr = 1;
			}
		} else {
			// 其他设备下，仍旧使用1倍的方案
			dpr = 1;
		}
		scale = 1 / dpr;
	}

	docEl.setAttribute('data-dpr', dpr);
	if (!metaEl) {
		metaEl = doc.createElement('meta');
		metaEl.setAttribute('name', 'viewport');
		metaEl.setAttribute(
			'content',
			'initial-scale=' +
				scale +
				', maximum-scale=' +
				scale +
				', minimum-scale=' +
				scale +
				', user-scalable=no'
		);
		if (docEl.firstElementChild) {
			docEl.firstElementChild.appendChild(metaEl);
		} else {
			var wrap = doc.createElement('div');
			wrap.appendChild(metaEl);
			doc.write(wrap.innerHTML);
		}
	}

	function refreshRem() {
		var width = docEl.getBoundingClientRect().width;
		// 最小1366px，最大适配2560px
		// if (width / dpr < 1280) {
		// 	width = 1280 * dpr;
		// } else if (width / dpr > 2560) {
		// 	width = 2560 * dpr;
		// }
		// 设置成24等份，设计稿时1920px的，这样1rem就是80px
		var rem = width / 24;
		docEl.style.fontSize = rem + 'px';
		flexible.rem = win.rem = rem;
	}

	win.addEventListener(
		'resize',
		function() {
			clearTimeout(tid);
			tid = setTimeout(refreshRem, 300);
		},
		false
	);
	win.addEventListener(
		'pageshow',
		function(e) {
			if (e.persisted) {
				clearTimeout(tid);
				tid = setTimeout(refreshRem, 300);
			}
		},
		false
	);

	if (doc.readyState === 'complete') {
		doc.body.style.fontSize = 12 * dpr + 'px';
	} else {
		doc.addEventListener(
			'DOMContentLoaded',
			// eslint-disable-next-line no-unused-vars
			function(e) {
				doc.body.style.fontSize = 12 * dpr + 'px';
			},
			false
		);
	}

	refreshRem();

	flexible.dpr = win.dpr = dpr;
	flexible.refreshRem = refreshRem;
	flexible.rem2px = function(d) {
		var val = parseFloat(d) * this.rem;
		if (typeof d === 'string' && d.match(/rem$/)) {
			val += 'px';
		}
		return val;
	};
	flexible.px2rem = function(d) {
		var val = parseFloat(d) / this.rem;
		if (typeof d === 'string' && d.match(/px$/)) {
			val += 'rem';
		}
		return val;
	};
})(window, window['lib'] || (window['lib'] = {}));
